Clinical and dosimetric predictors of physician and patient reported xerostomia following intensity modulated radiotherapy for nasopharyngeal cancer - A prospective cohort analysis.

BACKGROUND AND PURPOSE: To compare physician and patient reported xerostomia and correlate xerostomia with dosimetric and clinical parameters for nasopharyngeal cancer (NPC) patients treated with intensity modulated radiotherapy (IMRT) and chemotherapy. PATIENTS AND METHODS: We analyzed the data of 172 patients with locally advanced NPC. Xerostomia was evaluated via physician-rated xerostomia based on RTOG morbidity score (E1), patient-rated dry mouth (E2) and patient-rated sticky saliva (E3) based on EORTC QLQ-HN35 questionnaire. Primary endpoint was the presence of moderate to severe xerostomia at 2-year after completion of IMRT. RESULTS: The levels of physician reported xerostomia (E1) were consistently lower than patient reported dry mouth (E2) over time. The incidence of patients with xerostomia at 3-month post RT was 58% based on E1, 70% based on E2, and 51% based on E3. The corresponding incidence rates at 2-year post RT was 26% (E1), 36% (E2) and 21% (E3). The incidence of patients with xerostomia at 1-year post RT was close to that at 2-year post RT for all the 3 endpoints. The average Dmean of parotid glands was 41.5 Gy (range: 31.0 Gy-65.9 Gy, median: 40.7 Gy). No dosimetric parameters were significantly associated with xerostomia. CONCLUSION: Significant proportion of patients still experienced long term xerostomia with IMRT. Dose-effect relationships between xerostomia and the parotid glands were not observed in this study.

Reduction of intra-fraction prostate motion - Determining optimal bladder volume and filling for prostate radiotherapy using daily 4D TPUS and CBCT.

BACKGROUND AND PURPOSE: Inconsistent bladder and rectal volumes have been associated with motion uncertainties during prostate radiotherapy. This study investigates the impact of these volumes to determine the optimal bladder volume. MATERIALS AND METHODS: 60 patients from two Asian hospitals were recruited prospectively. 1887 daily cone-beam computed tomography (CBCT) images were analysed. Intra-fraction motion of the prostate was monitored real-time using a four-dimension transperineal ultrasound (4D TPUS) Clarity® system. The impact of planned bladder volume, adequacy of daily bladder filling, and rectum volume on mean intra-fraction motion of the prostate was analysed. Patients' ability to comply with the full bladder hydration protocol and level of frustration was assessed using a questionaire. Acute side effects were assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 3.0 and quality of life (QoL) assessed using the International Prostate Symptom Score (IPSS). RESULTS: The mean (SD) bladder and rectum volumes achieved during daily treatment were 139.7 cm3 (82.4 cm3) and 53.3 cm3 (18 cm3) respectively. Mean (SD) percentage change from planned CT volumes in bladder volume was reduced by 8.2% (48.7%) and rectum volume was increased by 12.4% (42.2%). Linear Mixed effect model analysis revealed a reduction in intra-fraction motion in both the Sup/Inf (p = 0.008) and Ant/Post (p = 0.0001) directions when the daily bladder was filled between 82 and 113% (3rd Quartiles) of the planned CT volumes. A reduction in intra-fraction motion of the prostate in the Ant/Post direction (z-plane) (p = 0.03) was observed when the planned bladder volume was greater than 200 ml. Patients complied well with the hydration protocol with minimal frustration (mean (SD) scores of 2.1 (1.4) and 1.8 (1.2) respectively). There was a moderate positive correlation (0.496) between mean bladder volume and IPSS reported post-treatment urinary straining (p = 0.001). CONCLUSIONS: A planned bladder volume >200 cm3 and daily filling between 82 and 113%, reduced intra-fraction motion of the prostate. The hydration protocol was well tolerated.

Thyroid V40 Predicts Primary Hypothyroidism After Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma.

PURPOSE: To investigate the various clinical and thyroid dosimetric parameters that could predict the risk of primary hypothyroidism (HT) after intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) and to determine useful thyroid dose constraints to guide radiation therapy planning. METHODS AND MATERIALS: From September 2009 to August 2012, 102 clinically euthyroid NPC patients were included in this study. All patients were treated with IMRT and randomized to induction chemotherapy followed by concurrent chemo-IMRT or concurrent chemo-IMRT alone. Thyroid function was evaluated by measuring thyroid-stimulating hormone and free thyroxine at each annual follow-up visit. Various clinical and dosimetric parameters (eg, V40 [percentage of thyroid volume receiving >40 Gy]) were obtained. Univariate and multivariate logistic regression analyses were performed to identify predictors of HT. RESULTS: Median follow-up was 48.8 months. Among the 102 patients, 44 (43.1%) developed HT within 2 years after radiation therapy. The median time to HT was 36.7 months (range, 24.9-49.0 months). The 1-year and 2-year cumulative incidence rates of HT were 33% and 44.5%, respectively. Univariate analysis revealed that younger age, early T stage, minimum dose to the thyroid gland, V40, and V45 were associated with HT. On multivariate analysis, younger age (P=.017), early T stage (P=.005), and V40 (P=.009) remained statistically significant. Patients with V40 > 85% had significantly higher cumulative incidence rates of HT than patients with V40 ≤ 85% (P=.007). CONCLUSIONS: Thyroid V40 is predictive of primary HT after IMRT for NPC, and V40 ≤ 85% can be a useful dose constraint to adopt during IMRT planning without compromising tumor coverage.